Certainly sandalwood oil is still nowdays one of the most precious elements to perfumers, not only for its intrinsic odorous characters, but also for the fixative properties it develops vis-a-vis a great variety of compositions of various nature. The prior art reports several synthetic products whose odorous properties can be assimilated to those shown by the natural oil. In this context, U.S. Pat. No. 4,052,341 describes a perfume composition consisting of a mixture of 3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)-pentane-3-ol and of 6-(2,2,3-trimethylcyclopent-3-en-1-yl)-hexan-3-ol, two alcohols of formula ##STR3##
DRG Pat. No. 68,936 describes compounds of formula ##STR4##
The two former compounds possess an odor reminiscent of musk and sandalwood oil whereas the latter compound develops an odor reminiscent of fig with a slight cedarwood tonality.
A thorough investigation relative to the sandalwood type compounds has been published by E. J. Brunke and E. Klein [Essential Oils, Ed. B. D. Mookherjee and C. J. Mussinan, p. 83 and ff., Allured Publishing Corp. (1981)]. From this study, it becomes apparent that one of the efficient synthon for the preparation of this type of compounds is constituted by campholenic aldehyde of formula ##STR5##
This molecular moiety is in fact present in many of the prior art compounds.
Naipawer et al. [Essential Oils, op, cit, p. 105 and ff] investigated the possible relationship which could exist between molecular structure and sandalwood odor of some of the prior known compounds.
Their study was intended to identify the "structural" characters a given chemical must possess in order to develop the desired sandalwood oil odor.
It is interesting to note in this respect that none of the compounds examined by Naipawer et al. possesses a double substitution at the carbon in position 2 of the open chain. On the other hand, none of the described compounds possesses a substitution at the carbon atom in position 4 of the same open chain.
Several fragrance specialities have been created by using the cited prior known compounds and have appeared on the market in the course of the last few years under different tradenames. These are depicted hereinbelow.
______________________________________ Formula of the main Speciality Origin constituent ______________________________________ SANDALORE L. Givaudan ##STR6## SANDACORE Kao Soap ##STR7## BRAHMANOL Dragoco ##STR8## BACDANOL Int. Flavors & Fragrances ##STR9## ______________________________________
In view of the already existing compounds, one might have believed that perfumers possess, for their creation activity, a sufficiently broad spectrum of sandalwood fragrant raw materials.
In reality, it has become apparent that such is not the case. If it is true to say that each of the prior known compounds is able to confer a sandalwood note to the compositions into which it is incorporated, the specific effects achieved vary widely from one compound to the other. Their diffusiveness, for example, as wellas their substantivity can also vary as a function of the particular application to which they are destined. Though they all have been defined as sandalwood type compounds, none of them possess an identical odor character. The expert recognizes in fact that the typical sandalwood oil note is but the resultant of a number of different odorous notes reminiscent in turn of santalol, cedarwood oil or gaiac-wood oil, or of sweet, balsamic, slightly ambery, spicy, animal or transpiration-like notes or even of those milky notes reminiscent of freshly boiled milk.
It doesn't come as a surprise therefore to find that none of the known compounds suggested by the prior art can, when taken alone, replace natural sandalwood oil, each of them contributing to a greater or lesser extent to one or the other of its specific partial characters. This fact may sound astonishing when looking at the analogy, from the point of view of their structure, presented by the above cited known derivatives of campholenic aldehyde. This confirms once again the character of uncertainty which surrounds any speculation in the field of aroma chemicals where no known theory enables to correlate validly the molecular structure of a given chemical and its odor properties.
It should be mentioned moreover that in the case of "sandalwood" compounds, marked effects of anosima have been observed among both expert and lay people; several individuals in fact were not able to detect the odor developed by one or the other of the compounds submitted to their evaluation.
As a result of this situation, there is a permanent need to develop novel compounds of sandalwood fragrance character in order to enlarge the perfumer's palette and to enable him to broaden his creative skill.